On 26.05.2022 03:18, Stefano Stabellini wrote: > On Wed, 25 May 2022, Jan Beulich wrote: >> On 25.05.2022 02:35, Stefano Stabellini wrote: >>> From: Stefano Stabellini <[email protected]> >>> >>> Add Rule 5.1, with the additional note that the character limit for Xen >>> is 63 characters. >>> >>> The max length identifiers found by ECLAIR are: >>> >>> __mitigate_spectre_bhb_clear_insn_start >>> domain_pause_by_systemcontroller_nosync >>> >>> Both of them are 40 characters long. A limit of 63 characters work for >>> the existing code. >> >> I have to admit that it hasn't become clear to me why we want to >> permit (if not to say encourage) the use of such long identifiers. >> If 40 is the longest we've got, why not limit it to 40 for now >> with a goal of further reducing? A 40-char symbol plus some >> indentation will already pose problems with 80-char line length. > > We can go lower than 63 if we want to. I chose the closest power-of-two > length -1 for the NUL terminator. But it doesn't have to be a > power-of-two. So we could go with "41" if we want to. > > Anyone in favor of that? I am happy with any number between 41 and 63.
Why 41, not 40? 41 seems yet more arbitrary to me than e.g. 40. >> Otoh, as said on the call, I think the public headers want >> mentioning explicitly here in some way. Part of them (most or all >> of what's under io/) aren't used when building Xen, so won't be >> seen by Eclair (aiui). Yet they are a formal part of the code >> base, and e.g. ring.h has some pretty long names (albeit still >> below 40 chars as it looks). So once we're able to go down to e.g. >> 32 for the bulk of the code base, public headers should imo still >> be explicitly allowed to use longer identifiers. > > Actually I thought about writing something for the public header but I > wasn't sure what to write. What about: > > - Note: the Xen characters limit for identifiers is 41. Public headers > (xen/include/public/) are allowed to retain longer identifiers for > backward compatibility. Fine with me, except I wonder in how far going forward we actually need to play by that limit there. Proper name-spacing is particularly important in the public headers, so may warrant a higher limit for certain (unusual?) circumstances. Jan
